This Study will be a small randomized trial (n=40 per group) comparing the clinical effectiveness of mechanical instrument assisted manipulation (MIAM) with traditional manual thrust manipulation (MTM) for the treatment of low back pain (LBP). Systematic reviews of the literature have described at least 42 randomized trials using spinal manipulation as a treatment for LBP, the majority of which utilized some variety of MTM but no high quality studies utilizing MIAM. This trial mil explore the differences in clinical effectiveness of these two manipulative methods for LBP. Eighty patients with a new onset of LBP within the past 12 weeks will be recruited and randomized into two groups; treatment with MTM or treatment with MIAM. ITie treatment frequency will be twice per week for 4 weeks (8 visits in total). Outcome measures will be gathered at 4,12, and 24 weeks. The primary outcome measure will be the Oswestry Disability Questionnaire (ODQ) score at 4-weeks. The secondary outcome measure will be the Numeric Pain Rating Scale (NPRS). Other secondary variables of interest will include treatment expectancy for each type of manipulation, fear-avoidance beliefs score, and presence of predictor variables from previously validated clinical prediction rules associated with manipulation and stabilization exercise successes. The primary analysis will be a generalized Imear regression model with 6-week ODQ score as the dependent variable and treatment group as the key independent variable; while controlling for baseline randomization variables and treatment expectation scores as covariates in the model. The secondary analysis will be a shnilar regression model using NPRS score as the dependent variable. The key aims of this study are; (1) to acquire infonnation that will be used to design a large clinical trial (ROl) on the comparative effectiveness of different types of spinal manipxUation and to determine its feasibility, and (2) to obtain parameter estimates of effect sizes and explore potential confounders or treatment effect mediators for the future larger trial.